The instant inventon relates to the mounting of photographs and the like and more particularly to a method of making pages for photo albums and to a page thereby formed.
While a variety of different types of pages have been heretofore available for mounting photographs and the like in albums, one particular type of page comprising a pair of flexible transparent plastic sheets which are heat sealed together along a plurality of seam lines has been found to be highly popular and effective. The heretofore available pages of this type have generally comprised a pair of sheets made of PVC plastic having thickness of approximately 3 mils. The sheets thereof have generally been heat sealed together along three or four spaced substantially parallel seam lines which define the top and bottom edges of their respective pages and which also define a plurality of transversely extending compartments therein for receiving and positioning photographs and the like between the sheets thereof. Pages of this type have frequently also included strips of paper or the like in the compartments thereof for providing backgrounds for photographs received in the compartments. Unfortunately, however, because it has generally been necessary to utilize relatively expensive plastic materials, such as PVC having thicknesses of at least 3 mils., for the sheets of pages of this type, the heretofore-available pages of this type have generally been relatively expensive. In many cases it has been found that it is necessary to treat the sheets of pages of this type with corona treatments in order to enable them to be effectively bonded by heat sealing. Accordingly, the sheets which have been utilized in the heretofore-available pages for photo albums of the above-described type have generally been relatively expensive; and because they have had thicknesses of at least 3 mils. and they have required corona treatments, they have often lacked clarity. Further, while automated processes have been heretofore available for manufacturing continuous strips of connected pages, these processes have been limited to relatively slow production rates by the heat sealing steps thereof. Still further, while attempts have been made to manufacture pages for photo albums of this general type by sonically welding sheets of transparent plastic materials together instead of by heat sealing the sheets, it has been found that pages made by this method have had similar disadvantages. In addition, it has been found that seams which are made in thin plastic sheets by sonic welding processes are often weak and lack durability and that when plastic sheets are sonically welded together, hazardous gases are often produced which are environmentally unacceptable.
The instant invention provides an effective page for a photo album and an effective method of making pages which have substantial advantages over the heretofore available pages and methods. Specifically, the instant invention provides a method which can be effectively utilized for making pages for photo albums from thinner, less expensive sheet materials having higher degrees of clarity, and the method can also be effectively applied in high-speed processes for rapidly making large quantities of pages. In this regard, the method of the instant invention comprises the steps of passing a continuously moving first elongated continuous sheet of flexible transparent plastic material through a work station, and continuously extruding at least two spaced narrow streams of a liquified hot-melt pressure-sensitive adhesive onto the first sheet to form at least two narrow, spaced, longitudinally extending lines of adhesive thereon. The method further comprises the steps of continuously overlaying a continuously moving second elongated continuous sheet of flexible transparent plastic material is substantially aligned relation on the first sheet so that the second sheet contacts the lines of adhesive, and pressing the first and second sheets together to secure them together along the lines of adhesive so that they form a continuous composite sheet, and thereafter transversely cutting the composite sheet at predetermined intervals to form pages for a photo album or the like. The first and second sheets preferably comprise biaxis-oriented polypropylene sheets having thicknesses of less than approximately 2 mils., and the pressing step is preferably carried out by passing the two sheets between a pair of rollers to press them together. The adhesive which is utilized in the method preferably comprises a hot-melt pressure-sensitive adhesive having a melting point of between 120.degree. F. and 350.degree. F. and having a viscosity of less than 2500 cp. at 350.degree. F., and the adhesive is preferably extruded at a temperature of approximately 325.degree. F. The sheets are preferably moved at a speed of greater than 100 ft./min. so that the adhesive is rapidly cooled by the air, and the adhesive is preferably cooled to a temperature of less than 120.degree. F. within less than five seconds from the time that it first contacts the first sheet and preferably before the second sheet is overlayed on the first sheet.
It has been found that the method of the instant invention can be effectively carried out utilizing biaxis-oriented polypropylene sheets having thicknesses of less than approximately 2 mils. In this connection, heretofore it has generally been considered to be impossible to effectively secure sheets of this type together by heat sealing, but it has now been found that instead they can be effectively secured together with a pressure-sensitive adhesive of the type hereinabove specified. In this regard, since the cost of biaxis-oriented polypropylene sheet material having a thickness of 1.8 mils. is approximately 40% of the cost of PVC sheet material having a thickness of approximately 3 mils., substantial material savings are realized when pages are made in accordance with the method of the instant invention. Further, since biaxis-oriented polypropylene sheets having thicknesses of less than 2 mils. have substantially improved clarity, the pages made by the method of the instant invention also have improved clarity. Still further, since the sheets of pages made by the method of the instant invention are secured together with a pressure-sensitive adhesive, if one of the seams on a page becomes damaged so that the sheets of the page can be separated, the seam can easily be repaired by pressing the two sheets together in the area of the damaged seam.
Accordingly, it is a primary object of the instant invention to provide an improved method for manufacturing pages for photo albums and the like.
A further object of the instant invention is to provide a method for manufacturing pages for photo albums at a reduced cost.
An even further object of the instant invention is to provide a method of manufacturing pages for photo albums and the like utilizing sheets of biaxis-oriented polypropylene.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.